In many surgical procedures, surgeons use a technique which employs a non-needled suture and an eyed needle. The needle is threaded by the nurse and the surgeon takes one pass through the tissue using a needleholder. He slips the needle off the suture, returns the needle to the nurse, and is ready for another threaded needle from the nurse. An assistant follows behind and ties the suture.
Surgeons find that this technique is more simple than using a needled item and cutting the suture with a scissors after each pass. However, the time required for threading results in a significant waste of expensive operating room time.
The security of attachment of eyeless needles to absorbable surgical sutures or to nonabsorbable surgical sutures is prescribed in the U.S. Pharmacopoeia, Vol. XVIII at Page 944 (also see U.S. Pharmacopoeia, Vol. XVII, Page 919). It has been the practice of suture manufacturers in the United States and abroad to securely attach the suture to the needle by swaging or with an adhesive so that the minimum pull-out standard recited in the U.S. Pharmacopoeia is met or exceeded. The conversion of the U.S. Pharmacopoeia minimum standard on needle attachment from kilograms to ounces is summarized in the following table.
______________________________________ MINIMUM LIMITS ON NEEDLE ATTACHMENT ______________________________________ AVERAGE INDIVIDUAL SIZE Kg. Oz. Kg. Oz. ______________________________________ 8/0 0.068 2.39 0.036 1.26 7/0 0.091 3.20 0.045 1.58 6/0 0.168 5.92 0.082 2.89 5/0 0.226 7.97 0.113 3.98 4/0 0.453 15.97 0.226 7.97 3/0 0.679 23.63 0.318 11.21 2/0 1.1 38.8 0.453 15.96 1/0 1.5 52.896 0.453 15.96 1 1.8 63.48 0.590 20.81 2 & larger 1.8 63.48 0.680 23.98 ______________________________________
It will be noted from the above table that separation of the suture from the needle is relatively easy if the suture is size 5/0 or smaller since the average force required is less than 8 ounces. On the other hand, the minimal average force required to separate a size 4/0 suture (diameter 7.0 mils. to 9.5 mils.) from the needle is at least about 16 ounces and because needles are swaged to make quite certain that the minimum U.S. Pharmacopoeia standards are met, many individual samples require forces in excess of 2 pounds to detach the needle from the suture.
There is a need for a needle-suture combination that has the convenience of the needle being preattached to the suture and yet permits separation of the needle from the suture without the necessity of cutting with a scissors.
One approach to this problem is described in copending Application Ser. No. 252,176, filed May 11, 1972 (ETH-363). This approach involves manufacturing the needle with an open channel at the blunt end thereof sized to receive a suture. The suture is bonded to the channel with an adhesive that prevents "pull-out" of the suture as it passes through tissue. After suturing, the surgeon may easily remove the needle from the suture by turning the needle so that the channel is at an angle of about 90.degree. to the direction of the suture and peeling the suture out of the channel.
This approach has one disadvantage in that many surgeons prefer a drilled needle over a channel needle because of the uniform cross-section at the end of the needle and the smooth transition between the needle and the attached suture.
Needle-suture combinations manufactured in accordance with the present invention are characterized by an average suture pull-out value substantially lower than the minimum average force specified in the U.S. Pharmacopoeia. Moreover, as will be described hereinafter, changes have been made in the manufacturing processes whereby the variation of the pull-out value from the mean is reduced.
It is an advantage of the product of the present invention, therefore, that the surgeon may readily remove the needle from the suture by exerting a force of 3 to 26 ounces and thereby save the time previously required to cut the suture.
The present invention is directed to needlesuture combinations wherein the suture is of large size, i.e., size 4/0 and larger (diameter greater than 7.0 mils.). The average pull-out value of the needle-suture combinations of the present invention is less than that required by the U.S. Pharmacopoeia and the needle may be removed from the suture by a straight pull of 3 to 26 ounces.
In accordance with the present invention, a needle-suture combination characterized by suture "pull-out" value between 3 ounces and 26 ounces and having a substantially uniform cross-section is manufactured by sizing one end of a braided suture with a resin; inserting the sized end of the suture into a drilled needle or preclosed channel needle and swaging the needle to predetermined dimensions. By proper control of the diameter of that end of the suture which is placed in the needle, the diameter of the needle hole and the swaging process, the needle-suture combination produced will have a suture pull-out value between 3 ounces and 26 ounces. It has been noted that if the bond between the needle and its attached suture is sufficient to withstand stand a pull of 3 ounces, the suture will not separate from the needle as a surgeon passes the needle through tissue. Yet, the needle can easily be removed from the suture at any time by simply pulling on the needle with a force of about 26 ounces.
It is an object of the present invention, therefore, to make available to the surgeon a needle-suture combination useful in suturing, and characterized by a needle-suture attachment that will permit facile removal of the needle from the suture without cutting the suture with a scissors.
Another object of this invention is to provide the surgeon with a needle-suture combination that will reduce the time that the surgical patient must spend in the operating room.
Yet another object of the invention is to provide the surgeon with a needle-suture combination that will permit separation of the needle from the suture after suturing by a slight pull upon the needle.
To achieve a controlled pull-out value of a needlesuture combination that is no less than about 3 ounces nor more than about 26 ounces, it is important that the physical dimensions of the needle, the hole in the end of the needle, and the diameter of the suture be uniform. The manufacture of surgical needles to precise dimensions has been done for many years, and it is well within the skill of the art to control the diameter of the needle and the size of the drilled hole to .+-. 0.0005 inches. The suture that must be attached to the needle, however, presents a more difficult problem. In the case of a synthetic monofilament suture, for example, the diameter may vary with the spinning, drawing, or annealing conditions. Braided sutures and covered sutures present a more difficult problem as the construction of the braid and adjustment of the braider compound any variability that may be present in the yarn. Moreover, the end of a braided or covered suture has a characteristic not found in monofilament sutures in that it will "broom" or open upon cutting. Since it is this cut end of a braided suture that is inserted into the drilled needle hole, it is necessary to hold the diameter of the suture end to within tolerances similar to that for the drilled needle hole to assure a "pull-out" force with a narrowlydefined range. In accordance with the present invention, the diameter of a braided suture may be carefully controlled by winding the braided strand on a rack under tension and immersing that section of the suture strand which is to be cut for insertion into the needle in an adhesive or bonding resin while maintaining the strand under tension. The rack is then removed from the resin solution and air dried. The dried adhesive composition which coats and impregnates the braided suture stabilizes the diameter to that achieved under tension. The binding resin or adhesive prevents "brooming" when the suture is cut and the diameter of the suture does not change even after the tension is relaxed.
The suture utilized in the present invention may be absorbable, i.e., catgut, extruded collagen, a braided polyhydroxyacetic ester, a synthetic copolymer of L(-) lactide and glycolide; or nonabsorbable, i.e., braided silk, nylon, polypropylene, cotton, linen, or polyester.
The adhesive that is used to coat the suture while it is retained under tension may be any non-toxic adhesive composition, either organic, inorganic or a hybrid. Suitable organic materials are such natural products as starch, dextrin, asphalt, animal and vegetable proteins, natural rubber, shellac; semi-synthetic products such as cellulose nitrate and the other cellulosics, polyamides derived from dimer acids, castor-oil based polyurethanes; such well-known synthetic resins as vinyl-type addition polymers, both resins and elastomers: polyvinyl acetate, polyvinyl alcohol, acrylics, unsaturated polyesters, butadiene/acrylonitrile, butadiene/styrene, neoprene, butyl rubber, polyisobutylene; and polymers formed by condensation and other step-wise mechanisms, i.e., epoxies, polyurethanes, polysulfide rubbers, and the reaction products of formaldehyde with phenol, resorcinol, urea, and melamine. Particularly preferred as bonding compositions are the epoxide resins and polyester resins.